An electronic music synthesizer is a keyboard instrument capable of producing sounds with selected characteristics regarding such parameters as pitch (frequency), envelope (slope of attack and decay), and timbre (overtone structure). Although early synthesizers were monophonic in that they were capable of producing only one note at a time, polyphonic synthesizers have recently been developed such as is disclosed in U.S. Pat. No. 3,986,423.
As has been recognized in U.S. Pat. No. 3,981,218, synthesizers in the past have included a variety of programmable or adjustable functions, the variation of which results in changes in the quality of sound produced by the instrument. A difficulty is presented during the playing of such an instrument, however, when the player wishes to rapidly change from one sound quality to a different sound quality. In the past, the only way that such a shift could be made, if it involved changing more than a very few function parameters, was by the operator adjusting a series of manual controls until the parameters were changed as desired. This is in most cases a relatively time-consuming task and requires the attention of the player to each of the function controls, successively, so that it is not ordinarily possible for the player to continue to play the instrument while he is changing the configuration of the controls. Thus, the instrument can be configured to produce radically different sounds, involving the adjustment of several function controls, only at the beginning of a musical performance. Drastic and sudden changes in sound during the playing of a musical composition are not ordinarily possible, because of the need to manipulate the controls one-by-one.
In view of the foregoing, said U.S. Pat. No. 3,981,218 teaches a system for storing function presets for an electronic music synthesizer whereby any of a plurality of preselected functional configurations can be selected by operation of a single switch, rather than by manual adjustment of a plurality of manual controls. Although the system disclosed in said U.S. Pat. No. 3,981,218 certainly facilitates a player's ability to easily modify the synthesizer characteristics, it is limited in versatility being restricted to a finite number of stored groups of function presets.
Moreover, whereas said U.S. Pat. No. 3,981,218 addresses the player's problem associated with attempting to reconfigure a monophonic instrument, the problem is of course considerably compounded in a polyphonic instrument.
An exemplary polyphonic synthesizer comprises a unit marketed by Oberheim Electronics, Inc., Santa Monica, Calif., which includes multiple independent voice modules or channels. Each module includes two voltage-controlled oscillators (VCO's), a voltage-controlled filter (VCF), a voltage-controlled amplifier (VCA) and two envelope generators. Multiplexer logic, as is disclosed in said U.S. Pat. No. 3,986,423, responds to a common keyboard to assign and distribute the independent keyboard control voltages (CV's) to the multiple voice modules. The multiplexer continually searches the keyboard at high speed to detect when a note has been played, and directs control voltages to a voice module as determined by keyboard logic, and the settings of keyboard switches.